Radio frequency switch apparatus



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MM 6 W uwm w. L. CORTEGGIANO ETAL RADIO FREQUENCY SWITCH APPARATUS Filed Oct. 27, 1950 Fig.2.

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J Aug. 25, 1953 Patented Aug. 25, 1953 RADIO FREQUENCY SWITCH APPARATUS William L. Corteggiano andJohn A. Redmond, Baltimore, Md., assignors to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application October 27, 1950, Serial No. 192,540

Our invention relates to a high frequency electrical circuit interrupter and, more particularly, to, a circuit breaker for use with radio frequency currents.

In accordance with the circuit breakers of the prior art, with which we are familiar, theinterruption of particularly radio frequency currents presents a difficult problembecause the objecjtionable arcing effects of radio-frequency currents have a tendency to burn out the contact members. This is particularly true when switching currents between 10,000 cycles and 450 kilocycles or greater. A further objection to the prior art switches is the tendency for them to become objectionably heated when continuous radio-frequency currents have to be handled for any appreciable period of time.

Accordingly, it is an object of our invention to provide a circuit interrupter which is adapted for interrupting radio-frequency currents. It is another object of our invention to providea circuit interrupter which is capable of carrying very high currents having radio frequencies.

It is still another object of our invention to provide a circuit interrupter which will not overheat when carrying currents in the range of 2500 amperes at 10,000 cycles and 800 amperes at 450 kilocycles.

It is still another object of our invention to provide a circuit interrupter which will substan- 'tially obviate contact troubles that result from arcingand corrosion of the contact surfaces.

Itisa still further object of our invention to provide a high-frequency and high-current electrical circuit interrupter which is simple in design and manufacture, and in which the contacts can be replaced easily when necessary.

In accordance with our invention, we provide a high-frequency electrical circuit interrupter which is suitable for switching relatively large currents having frequencies in the order of 10,000 cycles to 450 kilocycles and even greater, in which the contacts and current-carrying portions of the switch do not overheat with currents in the order of 2500 amperes at 10,000 cycles and 800 amperes at 450 kilocycles. Our switch comprises at least a, first and a second contact member with a rela-- tively flexible bridging contact member adapted to be ositioned therebetween. On the surface of the bridging contact member, nearest the said first and second contacts, there is a layer or coating of very highly conductive material, such as metallic silver. When the bridging contact member is positioned such that the conductive coating effectively bridges an electrical circuit 9 Claims. (01. 200-463) .between the two contact members, the greater portion of the current is carried by the two contact members, which are made of metallic copper,

.and the conductive coating on the flexible bridging contact member. The conductive coating extends lengthwise and beyond the ends of the flexible bridging contact member, to provide effective electrical shielding for it from the conducted currents, and therebysubstantially, prevents the induction heating of the bridging contact member itself. The opposite side of the bridging contact member, from that side or surface originally coated by the silver conductive material, may be coated with a second layer of silver conductive material to allow the whole switch to operate between a second pair of contact members. The use of a flexible bridging contact member, which may be made of spring steel, is desirable in that as the bridging contact member is positioned to close either one or the other of two electrical circuits, which it governs through one or the other conductive layer of ,metallic silver respectively, the flexible action of the bridging contact member allows it to bend slightly between the contact members. This results in a wiping action at the contacts between the respective contact members and the respective conductive coating of silver. This wiping or scraping action insures a good electrical contact at this point. The respective contact members are made of some metal such as copper, with a ihollowpassage therein for the conduction of cooling water through the entire length of each contact member. With the bridging contact member made of a spring steel leaf member and 4 aconductive coating of silver on each side thereof, the arrangement is such that most of the radio-frequency current flowsin the silver conductive layers to result in very little heating of the spring steel leaf member itself. What little heat is generated in the spring steel leaf member, due to the slight current which flows therein,

,is passed on to the silver conductive coating due to the excellent thermal contact therebetween. And any heating whichresults in the silver conductive coating is withdrawn by the stationary water-cooled copper contact members. The

bridging contact member may be slotted at its ends to provide a plurality of individual leaf-like contact surfaces to improve the electrical contact with said contact members.

The novel features that we consider characteristic of our invention are set forth with particularityin the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional adapted for one-way use to operate in a single electrical circuit.

In Figure 1 there is shown a bridging contact member I0 adapted to establish an electrical circuit between either a first I2 and second I4 contact member or a third I6 and fourth I8 contact member. An operating arm is bolted or similarly fastened to the bridging contact member I0 and. is used to move the bridging contact member ID into a first position between contact members l2 and I4, as shown by the upper dotted lines, or into a second position between contact members I6 and I8, as shown by the lower dotted lines. Each of the four contact members I2, I4, I6 and I8 comprises a tubular copper sleeve having a hollow passage 22 therein for the conduction of cooling water throughout the entire length of the respective copper sleeve. The bridging contact member Ill comprises a flexible spring steel inner member, 24 and a coating 26 or 28 of highly conductive material, such as silver, on each of the two major surfaces thereof.

In Figure 2 is shown a plan view of a portion of the circuit interrupter shown in Figure 1. Figure 2 shows the slotted sections 36, 38 and of the end construction of the bridging contact member Ill and the relative overlap of the highly conductive coating 26 placed on the one side of the flexible spring steel inner member 24. In dotted lines is shown the outline of one of the contact members I2, showing its relative length as compared to the width of the bridging contact member ID.

In Figure 3 is shown a contact member 30, which is similar to the contact members I2, I4, I6 or I8 shown in Figures 1 and 2. Here, however, the bridging contact member 32 is made up of a flexible spring steel member 34 with a conductive coating 31 of metallic silver on only one of the major surfaces of the latter member 34.

In the operation of the apparatus shown in Figure 1, the operating arm 20 can be controlled by any suitable mechanism (not shown), well known to those skilled in the art, to position the bridging contact member I0 in either the upper or the lower positions as shown to bridge an electrical circuit respectively between either the first I2 and second I4 contact members or the third I6 and fourth I8 contact members. As shown by dotted. lines, the operating arm 20 is moved through a distance greater than that necessary to merely touch the electrical contacts I2, I4, I6 0r I8 with the conductive coating 26 or 28. The operating arm 20 is given an additional movement, which is sufficient to flex the bridging contact member I!) and thereby provide a better electrical contact between the contact members I2 and I4 or I6 and I8 and the silver conductive coating 26 or 28 than would be obtained if the bridging contact member I0 were not flexed but was merely positioned'to touch the contact members I2 and I4 or IE and I8. In both the upper and lower positions, the operating arm 20 is pushed far enough to flex the bridging contact member I0 against the contact members I2 and I4 or I6 and I8. In this way there is a slight wiping or scraping motion between the contact members I2 and I4 or I6 and I8 and the silver conductive coating 26 or 28 to wipe away any corrosion or arcing effects from previous operations.

One application of the two-way-action circuit interrupter shown in Figure 1 would be to establish either a 10,000 cycle circuit between the first I2 and second I4 contact members or a 450 kilocycle circuit between the third I6 and fourth I8 contact members. Of course, the latter frequency figures are merely illustrative, and the circuit interrupter shown in Figure 1 is suitable to establish any electrical circuits having a wide range of frequencies between zero frequency and beyond 450 kilocycles of the radio-frequency range.

In the operation of the slotted sections 36, 38

and 40 of the bridging contact member In as shown in Figure 2, any surface irregularity along the length of any of the contact members I2, I4, I6 or I 8 will not cause serious operation difficulty. For example, if there is a high surface spot or a dirt particle on the first electrical contact member I2 in a position adjacent the middle section 38 on the bridging contact member I0, the center section 38 may leave the plane of the other sections 36 and 40. However, the operation of the other sections 36 and 40 will not be substantially interfered with, and the sections 36 and 40 will assume positions along the contact member I2 for good conduction of the established or interrupted electrical currents involved.

In the operation of the apparatus shown in Figure 3, the bridging contact member 32 is suitable to interrupt or establish an electrical circuit between but two contact members 30 (and another not shown). An operating arm (not shown) functions to establish a single electrical circuit from the shown contact member 30 through a conductive coating 31 on the one side of the flexible spring steel member 34 and to a second contact member (not shown). The apparatus of Figure 3 operates in a manner otherwise similar to that of Figure 1.

Although we have shown and described certain specific embodiments of our invention, we are fully aware that many modifications thereof are possible. For example, the conductive material need not be coated or fastened physically to the flexible spring steel member; separate strips or sheets of conductive material, such as a silver alloy, may be held in the proper position relative to the support of spring steel by a common bolt .or fastener through the combination, for instance at the end of the operating arm. Our invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and the spirit of the appended claims.

We claim as our invention:

1. In electrical current interrupter apparatus, the combination of a first and a second contact member, a third contact member adapted to electrically bridge said first and second contact members, said third contact member comprising a flexible member with a coating of highly conductive material placed on said flexible member, said coating being of suflicient length to extend between said first and second contact members when said third contact member is in position to bridge an electrical circuit between said first and second contact members to thereby carry the electrical currents therebetween.

2. The circuit interrupter as claimed in claim 1,

characterized by said flexible member being a flat strip of spring steel.

3. The circuit interrupter claimed in claim 1, characterized by said coating of said highly conductive material being a coating of metallic silver.

4. The circuit interrupter of claim 1 in which the conductive material is in the form of a separate sheet positioned adjacent said flexible member.

5. In apparatus for interrupting radio-frequency currents, the combination of a first and a second contact member, each of said first and second contact members having passages therethrough for the conduction of cooling fluid, and a third contact member adapted to cooperate with said first and second contact members, said third contact member comprisin a fiat strip of spring steel having a length greater than the distance between said first and second contact members, and a coating of highly conductive material on said spring steel strip, said coating of highly con ductive material extending physically throughout the whole length of said strip of spring steel and lengthwise beyond the ends of said strip.

6. The circuit interrupter as claimed in claim 5, characterized by said coating of highly conductive material being a coating of metallic silver.

7. The circuit interrupter claimed in claim 5, characterized by a second coating on said strip of spring steel, said second coating being of highly conductive material and on the side of said strip opposite the first coatin of conductive material, said second coating being of substantially the same physical length as the other coating.

8. The circuit interrupter of claim 7, characterized by said two conductive layers being of metallic silver.

9. The circuit interrupter of claim 7 in which each of said conductive materials is positioned on opposite sides of said spring steel strip and is in the form of a separate and independent member.

WILLIAM L. CORTEGGIANO. JOHN A. REDMOND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 803,486 Hill Oct, 31, 1905 1,039,011 Beck Sept. 17, 1912 1,157,960 Post Oct. 26, 1915 1,900,256 Payette Mar. 7, 1935 2,172,888 Lazick et a1. Sept. 12, 1939 

